Originally Posted by xdestry
Try pulling a bunch of the hairgrass out and see how far the runners have spread and whether any hairgrass has started growing up but not penetrated the surface yet.
You should also try and separate the hairgrass into individual stems, it will be much faster that way
I've pulled it up and a few plantlets have what I imagine are the beginnings of runners. I tried to split up into individual stems when I got it, I suppose I can try again...